1. Field of the Invention
The invention relates the field of light sources using light emitting diodes (LEDs) and in particular to an apparatus and a method of collecting the energy radiating from them. The device could be used in general lighting, decorative and architectural lighting, portable lighting, emergency lighting and many other applications. The invention is particularly useful when direct visibility to the intense light source is undesirable, such as is the case for a dentist's patient.
2. Description of the Prior Art
Most high brightness LED optical solutions exhibit a very annoying bright LED source, such that viewers in close proximity will be discomforted at best and distracted or even temporarily ‘blinded’ when they ‘look back’ at the apparatus. Several optical solutions place the LED behind a forward mounted reflector that reflects outward a portion of the forward solid angle light emitted by the LED and reflects it again substantially along the centerline into the original direction of the LED. The peripheral forward light from the LED, however is largely ignored or is directed out of the optic peripherally, not along the centerline. By empirical measurements the beam efficiency of this system and similar solutions can be less than 50%.
Another means seen in the prior art is the reflex reflector such as that taught in U.S. Pat. No. 7,001,047. This solution, while showing better efficiency is typically less than 70% beam efficient, depending on system aperture.
What is needed is an optic solution whereby efficient collection of almost all of an LED's radiated energy can be obtained and projected into an indirect beam with an illumination distribution that is useful.